Playground physics phun

I was at Barney Park recently riding on a swing and having a great time.

"Why don't more adults ride swings," I asked one of my older students—let’s call
him Newton.

"Because they look ridiculous," Newton replied.

I asked if I looked ridiculous and Newton said that I did not need to ride a swing
to look ridiculous.

I like Newton, so I decided not to bump him off his swing.

Despite Newtons’s accusation, I continued to ride the swing and thoroughly enjoyed myself while flying through the air.

As I sat there, I wondered why I moved forward when I pumped my legs and then went in reverse. Then I saw my students on the merry-go-round hanging on for dear life. I realized many of the toys on the playground can be explained using laws from Science. I had to share my excitement so the next time you take your children to Barney or Lockey or any other of Helena's great parks, you too can explain the science behind the swinging.

When I was growing up I would wait in line for my chance to defy gravity and feel as though I was flying on all of the park toys—from the swings to the slides. Was I really defying gravity or was I just altering the effect gravity had on me? Since my fascination appears to continue, I'll keep the focus on swings; but first gravity should be explained.

Gravity is much more complex than knowing what goes up must come down. It is the force of attraction between any two objects. Small objects and objects far away from each other do not have much attraction. Here in Helena, the force of attraction is humongous because Earth is so massive and we're close to the center. The farther we move away from the center of Earth though, the less attraction Earth has on us. This is why astronauts can space walk and why we actually weigh a little less when we climb Mount Everest.

When you sit on a swing, it's almost as if you're sitting on a pendulum, similar to a Newton’s cradle. If you throw your weight back while hanging onto the chains, this action causes a reaction of moving the swing forward. Once you reach your maximum height on one side, the attraction between you and Earth pulls you back down. Since you are on a pendulum, rather than smacking into the earth, your momentum is carried back to the other side.

We continue to swing until we stop putting work into it. Once we stop pumping our legs the swing eventually stops.  This is because friction from the air combined with gravity is too much to overcome.

I try to explain all this to my daughter when we go to  the park and she looks at me as if I am ridiculous. It must be because she's only two years old, because as far as I know she's never met Newton.